I'm working on a chart of the percentage chance of meeting or beating target numbers on various kinds of dice. I know this sort of thing has been done countless times before, so I'm hoping someone can point me toward either a chart or a program that can do the math for me on the more complex ones.

Basically, using from 1 - 6 dice, all of one size (d4, d6, d8 or d10), what are the chances to hit target numbers 5 - 10, 12, 20, 25, and 30?

I've figured out all the easy ones already, but I R NOT SMRT when it comes to the higher level math stuff.

Torben Mogensen has a big "examination and basics of probability theory in RPGs"-style PDF document up on his site that may prove helpful in figuring the question out for yourself, or it may just make you feel like you should climb back into the trees. Do note that while Torben is brilliant and there's good material in there, he's also definitely old-school in his preferences and viewpoints of the role of probabilities (and mechanics/attributes/etc) in a game.

He also provides Troll, a freeware program which calculates dice probabilities, and instructions on how to use it to find probabilities for various sets of rolled dice that should work quite well for you.

Or you could also just pop over to the RPG-Create group on Yahoo and ask Torben himself, who is usually lurking quietly waiting to spring from nowhere with his giant brain and number-filled notepad.

(But I should warn you, because I don't recall if you are or have been active over there, a number of the most vocal members of RPG-Create are deeply intolerant of "indie" -- or rather more accurately "non-Sim", as they make no distinction -- games, and even other more reasonable members don't tend to see any value or point in non-traditional designs or styles.)